public override byte[] Decode( MpegFrame frame, BitReader reader )
{
byte[,] allocation = new byte[subbands, 2];
byte[,] scaleIndices = new byte[subbands, 2];
channels = frame.Channels;
int[,,] samples = new int[samplesPerSubband, subbands, channels];
byte[] output = new byte[totalSamples * channels * 2];
this.reader = reader;
int index = 0;
if( frame.ChannelMode == ChannelMode.SingleChannel || frame.ChannelMode == ChannelMode.Stereo
|| frame.ChannelMode == ChannelMode.DualChannel ) {
ReadBitAllocation( allocation );
ReadScaleFactors( allocation, scaleIndices );
ReadSamples( allocation, samples );
for( int s = 0; s < samplesPerSubband; s++ ) {
double[,] bandTbl = new double[channels, subbands];
RequantiseSamples( s, bandTbl, allocation, samples, scaleIndices );
if( channels == 1 ) {
double[] samples0 = Common.SynthesisSubbandFilter( 0, bandTbl, V0, subbands );
for( int sb = 0; sb < subbands; sb++ ) {
Common.OutputSample( samples0[sb], output, ref index );
}
} else {
double[] samples0 = Common.SynthesisSubbandFilter( 0, bandTbl, V0, subbands );
double[] samples1 = Common.SynthesisSubbandFilter( 1, bandTbl, V1, subbands );
for( int sb = 0; sb < subbands; sb++ ) {
Common.OutputSample( samples0[sb], output, ref index );
Common.OutputSample( samples1[sb], output, ref index );
}
}
}
return output;
} else {
throw new NotImplementedException( "joint stereo implementation not done");
}
}
public abstract byte[] Decode( MpegFrame frame, BitReader reader );
public IEnumerable<AudioChunk> StreamData( Stream source )
{
info = new AudioChunk();
PrimitiveReader reader = new PrimitiveReader( source );
while( true ) {
// Read frame header
BitReader bitReader = new BitReader( reader );
bitReader.BigEndian = true;
//Console.WriteLine( "start pos" + reader.Position );
// Skip any padding('00') bytes before the start of a frame
byte data = 0;
while( ( data = reader.ReadByte() ) == 0 );
// Make sure that the 'data' byte is the first 8 bits of the sync word.
if( data != 0xFF ) {
throw new InvalidDataException( "Invalid frame sync value." );
}
int frameSync = bitReader.ReadBits( 3/*11*/ );
if( frameSync != 0x7/*FF*/ ) {
throw new InvalidDataException( "Invalid frame sync value." );
}
int versionId = bitReader.ReadBits( 2 );
int layerIndex = bitReader.ReadBits( 2 );
bool crcProtection = bitReader.ReadBit() == 0;
int bitrateIndex = bitReader.ReadBits( 4 );
int samplingRateIndex = bitReader.ReadBits( 2 );
bool padded = bitReader.ReadBit() != 0;
int privateBit = bitReader.ReadBit();
int channelMode = bitReader.ReadBits( 2 );
int modeExtension = bitReader.ReadBits( 2 );
int copyrightBit = bitReader.ReadBit();
int originalBit = bitReader.ReadBit();
int emphasis = bitReader.ReadBits( 2 );
int bitrate = GetBitRate( (MpegVersion)versionId, layerIndex, bitrateIndex );
info.Frequency = samplingRates[versionId][samplingRateIndex];
ushort crc = 0;
if( crcProtection ) {
crc = (ushort)bitReader.ReadBits( 16 );
}
MpegFrame frame = new MpegFrame();
frame.Bitrate = bitrate;
frame.ChannelMode = (ChannelMode)channelMode;
frame.Channels = Common.GetNumberOfChannels( frame.ChannelMode );
frame.CrcProtected = crcProtection;
frame.Padding = padded;
frame.ModeExtension = modeExtension;
frame.SampleRate = info.Frequency;
frame.Emphasis = emphasis;
frame.Version = (MpegVersion)versionId;
LayerIndex index2 = (LayerIndex)layerIndex;
info.Data = null;
//Console.WriteLine( "padding: {0}, type: {1}, sr: {2}, br: {3}",
//frame.Padding, index2, frame.SampleRate, frame.Bitrate );
if( layerIndex == (int)LayerIndex.Layer1 ) {
info.Data = decoder1.Decode( frame, bitReader );
} else if( layerIndex == (int)LayerIndex.Layer2 ) {
info.Data = decoder2.Decode( frame, bitReader );
} else if( layerIndex == (int)LayerIndex.Layer3 ) {
throw new NotSupportedException( "Layer III not supported" );
} else {
throw new InvalidDataException( "Invalid layer" );
}
info.Channels = frame.Channels;
info.BitsPerSample = 16;
//if( bitReader.offset == 8 ) {
//reader.ReadByte();
//}
yield return info;
}
}